In the dental clinical field and dental research, the dental structural materials such as orthodontic brackets, orthodontic instruments, inlays, onlays, bridges, core materials, implant upper structures, partial dentures, complete dentures, various casts, experimental jigs and experimental structural materials are manufactured by a complex method including many steps, which mainly combine manual mold making, production of replicated model, waxing-up, investing, dewaxing, mold, kneading, polishing, etc. In order to carry out this method, the correct knowledge for procuring a wide variety of materials and instruments and using and applying them in their suitable ways is essential. Further, adequate learning and skill are required for the operation. Accordingly, it is very laborious and time-consuming to manufacture the dental structural materials, so that there is a limit to the improvement of manufacturing efficiency and productivity. Also, since errors are inevitable due to several repetitions of mold making and casting processes, final products sometimes have unsatisfactory adaptability and color tones. In order to solve these problems, adjusting and modifying operations that need further skill, trouble and time have to be undertaken.
To address this issue, based on a computer processing technology that has advanced considerably in recent years, a large number of methods for improving the quality and production efficiency have been developed.
JP 2004-344623 A and JP 2005-59477 A describe layered-object forming apparatuses for forming powder into layers on a forming table so as to produce a desired three-dimensional structure. The following is a brief description thereof.
FIG. 26 is a perspective view showing a schematic configuration of a conventional layered-object forming apparatus 100. As shown in this figure, horizontal axes that are perpendicular to each other are indicated by an X axis and a Y axis, and a vertical axis is indicated by a Z axis. In FIG. 26, numeral 110 denotes a forming table that can be lifted and lowered in the Z-axis direction, numeral 120 denotes a container including a wall surrounding the horizontal periphery of the forming table 110, numeral 130 denotes a powder feeder that disperses powder on the forming table 110, numeral 140 denotes a liquid feeder that delivers a liquid on the forming table 110, numeral 150 denotes a leveling member that levels off an upper surface of the powder dispersed on the forming table 110, and numeral 160 denotes a light source that emits a light beam for photopolymerization of the delivered liquid. For easier understanding of the structure, in FIG. 26, the container 120 is indicated by chain double-dashed lines so that the forming table 110 therein is seen through it.
The powder feeder 130 has a powder dispersion width that is substantially the same as the dimension of the forming table 110 in the Y-axis direction. The powder feeder 130 moves in the X-axis direction while dispersing the powder, so that the powder is dispersed on an overall surface of the forming table 110.
The leveling member 150 has a lower end, which is provided with a leveling edge 151 extending in the Y-axis direction. The leveling member 150 moves in the X-axis direction while allowing the leveling edge 151 to slide on an upper surface 122 of the container 120.
The liquid feeder 140 is moved in the Y-axis direction by a uniaxial guiding mechanism 148. This uniaxial guiding mechanism 148 is driven in the X-axis direction by a driving mechanism, which is not shown in the figure. In other words, the liquid feeder 140 delivers the liquid toward the forming table 110 at desired positions while scanning along the X-axis and Y-axis directions over the forming table 110.
The forming table 110 is lowered at a constant pitch by a driving mechanism, which is not shown in the figure. The powder is formed as layers on the forming table 110, with the thickness of one layer corresponding to this single pitch.
The method for producing a three-dimensional structure will be described in detail with reference to FIGS. 27A to 27E.
FIG. 27A shows the state in which a plurality of layers (two layers in the figure) of the powder already are formed on the forming table 110. Numeral 171 denotes an uppermost layer in the plurality of powder layers deposited on the forming table 110, numeral 172 denotes a consolidated portion in the uppermost layer 171 formed by polymerizing the liquid, numeral 173 denotes a powder layer deposited immediately before the uppermost layer 171, and numeral 174 denotes a consolidated portion in the powder layer 173 formed by polymerizing the liquid.
In this state, as shown in FIG. 27A, while the powder feeder 130 is being moved in the X-axis direction, powder 134 is dispersed on the forming table 110 from a slit 132 of the powder feeder 130.
Next, as shown in FIG. 27B, the leveling member 150 is moved in the X-axis direction, thereby conforming an upper surface of the powder 134 so as to have the same height as the upper surface 122 of the container 120. In this manner, a powder layer 175 having a uniform thickness is formed on the uppermost layer 171.
Subsequently, as shown in FIG. 27C, while the liquid feeder 140 is being moved, the liquid is delivered toward the powder layer 175 at a desired position. Numeral 176 indicates a portion in the powder layer 175 to which the liquid is applied.
Thereafter, as shown in FIG. 27D, light is irradiated using the light source 160, thereby polymerizing and solidifying the liquid applied to the powder layer 175. When the liquid is solidified, the powder in a region to which the liquid has been applied is integrated. In this way, a consolidated portion 177 is formed in the powder layer 175.
Then, the forming table 110 is lowered by a predetermined pitch, and the processes of FIGS. 27A to 27D described above are carried out. The above-mentioned processes are repeated necessary times.
Finally, unconsolidated powder on the forming table 110 is removed, thus obtaining a three-dimensional structure 170 in which the consolidated portions 174, 172 and 177, etc. are integrated as shown in FIG. 27E.
By utilizing this method, it also is possible to produce three-dimensional structures with a complex shape, for example, dental structural materials.